Pyroelectric device



p 1954 J. D. HEIBEL 2,675,417

' PYROELECTRIC DEVICE Filed Aug. 14,1952

mum

3m entor Patented Apr. 13, 1954 UNITED STATES ATENT OFFICE PYROELECTRICDEVICE Jerome D. Heibel, Erie, Pa., assignor to Eric ResistorCorporation, Erie, Pa., a corporation of Pennsylvania Application August14, 1952, Serial No. 304,260

4 Claims.

This invention is a pyroelectric device which in a preferred formcomprises a stack of annular discs of pyroelectric material with the hotjunctions at the center or bore of the stack and the cold junctions atthe outside or periphery. This construction is particularly adapted todirect firing with fluid fuel where the combustion air can be utilizedto cool the cold junctions and the bore of the stack serves as a fluefor the hot gases which heat the hot junctions. The series connectionbetween the hot and cold junctions of adjacent pyroelectric discs can bemade by interleaved annular metal discs having contact making flanges atthe inner and outer parts thereof respectively offset in oppositedirections.

In the drawing, the single figure is a sectional elevation of a directfired pyroelectric device.

In the drawing, l and 2 indicate alternate pyroelectric and conductingannular discs or plates arranged in a stack to provide a pyroelectricdevice. The discs I and 2 are of substantially the same outside diameterand are stacked with central openings 4 and 5 in register so as toprovide a flue 6 for the products of combustion from a Bunsen burner 1arranged at the bottom of the flue. The Bunsen burner isdiagrammatically illustrated as comprising a gas inlet line 8discharging through a flow restricting orifice 9 to a nozzle to. Thenozzle is located adjacent combustion air inlet openings II at the lowerpart of a mixing tube l2. The flame appears at the upper end of thetube. Obviously, other burners may be used. With this arrangement, theinner peripheral edges of the center openings l in the annularpyroelectric discs I become the hot junctions of the discs and thelaterally spaced outer peripheral edges become the cold junctions. Theinterleaved metal discs 2 are arranged with ofiset flanges I3 and M atthe inner and outer parts thereof, which extend in opposite directionsand serve to connect the hot junction of one of the discs in the stackto the cold junction of the disc next lower in the stack.

With this arrangement the combustion air for the burner I can beutilized to maintain the required temperature differential between thehot and cold junctions of the pyroelectric discs. This is accomplishedby surrounding the stack with a duct or casing I having an air inlet H5at the top. At the center of the casing is a collar l1 which connectsthe upper end of the flue 6 to a stack I8. Heat insulation l9 arrangedaround the collar prevents preheating of the incoming air by theoutgoing flue gases. The incoming air flows down through an annularspace 20 surrounding the outer periphery of the stack to the bottom ofthe casing where the burner I is located. At the lower end of the flue 6there is a depending tube 2! which serves as a combustion chamber forthe burner. The tube 2| is surrounded by heat insulation 22 whichprevents cooling of the combustion chamber. By this arrangement, thecombustion air coming in through the inlet 16 is used to cool the coldjunctions of the pyroelectric discs I and the heat imparted to thecombustion air increases the temperature of the burner flame and therebymaintains the desired temperature difierential between the hot and coldjunctions of the discs.

The voltage output can be taken ofi between hot and cold junctions atthe top and bottom of the stack. The voltage takeoif is illustrated as alead 23 connected to the cold junction of the uppermost disc and a lead24 connected to the hot junction of the lowermost disc, the voltageoutput appearing across a voltmeter 25.

The pyroelectric discs I may be made of reduced titanium dioxideceramic. Such discs are made by subjecting fired titanium dioxideceramic (a dielectric) to a reducing atmosphere (e. g. hydrogen) at anelevated temperature for a suificient time to reduce the titaniumdioxide to a mixture of T102, TizOs, TiO. Upon reduction the discsbecome semi-conductors. The reduced discs also exhibit pyroelectriceffects of substantial magnitude. For example, a voltage of A1 of a voltcan readily be obtained for a temperature difierential between the hotand cold junctions of from 300 to 400 degrees centigrade. The 300 to 400degrees centigrade temperature differential is well within the operatingrange of th reduced titanium dioxide discs.

Reduced titanium dioxide ceramic discs have been heretofore made for useas resistors and their manufacture is well understood. The reducedtitanium dioxide ceramic is characterized by a dark blue to black coloras distinguished from the white of the unreduced titanium dioxideceramic. As is usual in the ceramic art, fluxes and binders are used tomake the green ceramic easier to work and to improve the density andother physical properties of the ceramic. These fluxes and binders likeother inert ingredients or impurities do not change the nature of thepyroelectric action of the reduced titanium dioxide ceramic discs.

What I claim as new is:

1. A pyroelectric device comprising a stack of annular discs of reducedtitanium dioxide ceramic, the central openings in the discs providing aflue, a fluid fuel burner discharging its products of combustion intoone end of the flue to provide hot junctions at the inner peripheries ofthe discs, a combustion air intake casing for the burner surrounding thediscs and drawing air over the outer peripheries of the discs to providecold junctions, and an electrical take-0E including electricalconnectors interleaved between the discs connecting the innerperipheries of the discs in series with the outer peripheries ofadjacent discs in the stack.

2. A pyroelectric device comprising a stack of annular discs ofpyroelectric material, the central openings in the discs providing afine, means for circulating a heating medium through the flue to providehot junctions at the inner peripheries of the discs, means forcirculating a coolant over the outer peripheries of the discs to providecold junctions, and an electrical takeofi including electricalconnectors interleaved between the discs connecting the innerperipheries of the discs in series with the outer peripheries ofadjacent discs in the stack.

3. A pyroelectric device comprising a stack of plates of reducedtitanium dioxide ceramic, a burner discharging its products ofcombustion over one edge of the stack to provide hot junctions at thecorresponding edges of the discs, a combustion air intake duct for theburner drawing air over a laterally spaced edge of the stack to providecold junctions at the corresponding laterally spaced edges of the discs,and an electrical take-01f including electrical connectors interleavedbetween the discs connecting the hot and cold junctions of discs inseries.

4. A pyroelectric device comprising a stack of plates of pyroelectricmaterial, means for circulating a heating medium over one edge of thestack to provide hot junctions at the corresponding edges of the plates,means for circulating a coolant over a laterally spaced edge of thestack to provide cold junctions at the corresponding laterally spacededges of the plates, and an electrical take-01f including metal platesbetween adjacent plates in the stack each having laterally spacedflanges respectively ofiset in o posite directions and respectivelymaking contact with the hot and cold junctions of the plates to connectthe hot and cold junctions in series.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 241,859 Higgs May 24, 1881 289,631 Eaton Dec. 4, 1883 824,684Cove June 26, 1906 903,116 Vokel Nov. 3, 1908 1,234,515 Webb July 24,1917 1,286,429 Schindel Dec. 3, 1918 2,415,005 Findley Jan. 28. 1947

